Flattery attended the College for Creative Studies in Detroit between 1982 and 1987 and graduated with a BFA in Design. Flattery has started his career in the entertainment industry in 1988 and worked on concept art for the vehicles in the science fiction sequel Back to the Future Part II (1989, starring Christopher Lloyd), for the Batmobile and Batboat in the comic adaptations Batman Returns (1992) and Batman Forever (1995), weapons design on the science fiction comedy Men in Black (1997) and its sequel Men in Black II (2002), the space station in the drama Solaris (2002), Doc Ock's tentacles in the sequel Spider-Man 2 (2004, starring Kirsten Dunst and with Donna Murphy), and the Fantasticar in the sequel 4: Rise of the Silver Surfer (2007).

Among his earlier works as color animations on the television series Captain N: The Game Master (1990), Swamp Thing (1991), and G.I. Joe (1991-1992), as well as concept design and illustration on the science fiction comedy My Stepmother is an Alien (1988), the science fiction thriller Total Recall (1990), the horror sequel Child's Play 3 (1991), the comic adaptation The Flintstones (1994), and the crime drama The Client (1994).

More recent work as Concept Designer include the science fiction adventure After Earth (2013), the reboot RoboCop (2014), the comic sequel Captain America: The Winter Soldier (2014), and Brad Bird's science fiction film Tomorrowland (2015, written and produced by Damon Lindelof, produced by Jeffrey Chernov, music by Michael Giacchino, and production design by Scott Chambliss).